The invention is based on a drill hammer or riveter as generically defined by the preamble to claim 1. From European Patent Disclosure EP-A 429 475, a drill hammer or riveter is known which has a guide tube supported axially displaceably in a housing. An axially reciprocating piston, which is coupled via an air cushion to a striker, is accommodated in the guide tube. A restoring spring urges the guide tube with a restoring force in the direction of a front outset position, in which the air cushion is ventilated via an opening in the guide tube, so that the hammering mechanism of the drill hammer or riveter goes into the idling mode and no further axial impacts are exerted on a tool. If the guide tube is forced axially rearward out of this position by the application of the drill hammer or riveter against a machining point counter to the prestressing force of the restoring spring, then the ventilation opening is closed, and the hammering mechanism enters the hammering position. In the riveting mode, via a riveting die the guide tube experiences reverse impacts, which are transmitted to the housing via the restoring spring. To the operator of the drill hammer or riveter, these reverse impacts are irritating, so that the attempt is made to avoid or reduce them as much as possible.
The drill hammer or riveter according to the invention having the characteristics of claim 1 has the advantage that the vibration caused by the hammering mechanism can be reduced in a relatively simple way.
By the provisions recited in the dependent claims, advantageous refinements of and improvements to the drill hammer or riveter according to the invention are possible.